Comments

This example only uses the camera and the 3D rendering, and tries to recognize what the camera sees in order to do overlaying. What I want to see is the combination of GPS (for rough position) and accelerometer (for direction finding) to render overlays that are intuitively recognizable just by pointing the phone. Perhaps image recognition could smooth over the rough edges.

I don't know how well it would work in practice, but it's worth a shot.